I am aghast at the 48" center floor joists!!!!!!!

24" center floor joists are not legal---much less double that!!!!!!!

If I were in your situation, I would add 2" by 6"s or 2" by 8"s between the existing joists to frame the bathroom area so you can install new a subfloor---I'd use pressure treated 3/4" plywood. Regular construction grade plywood would be fine also, but the PT would resist any future leakage better and once covered with flooring , pose no threat.(There is little threat anyway, but some folks feel differently.)

Unfortunately, you will have to get into that crawl space---to install the joist hangers on the joists to either side of the one in the bathroom space, but by precutting them and having a bright light----as well as having the old flooring in the bath completely removed---you mighht be able to handle being in the space------you could go in through the bath floor opening which would allow you to set a couple of hangers and stand up---that kinda thing.

"24" center floor joists are not legal"

Funny, the IRC shows 12, 16, 19.2 and 24 inch joist spacing.
If the house is older or engineered you can even go further.
The floor gets thicker with larger spacings, but they are very doable.

You are going to need to add joists one way or another.
I have even worked on older houses that had crawl spaces so short we had to dig out to get in them for work.
As long as you are well away from any piers or foundation supports you can dig.

Huh. My dad has been a framer for 40 some odd years and he wasn't surprised at all- the floor is VERY sturdy- I guess the 1x5 tongue and grove was the thing to do back in the day- think it is actually greater than 1", but not sure exactly. If you go under the house, which I won't, there are some big old beams and piers which is what all this flooring is resting on. It is def. not your standard 1x6 holding up the floor.

We've had fans on the stuff all night and it is dry now- I'm just wondering- how do you tell if omething is rotten? It isn't soft at all or anything, no splintering or chnks coming up. But I don't really know?

If you can stick a screwdriver through it, it is rotten.

If you have the room put pressure treated 3/4" plywood down over the subfloor and you should be good to go for another 50 years.

Thanks Hendrickus!

So, looks like the subfloor will not need to be replaced. It is solid as a rock and dried out quite nicely. I'm going to treat the wood and then lay exterior grade plywood down.

I went a little crazy and ripped most of the sheetrock off the walls. I demolished the vanity and the tile tub.shower surround. We're going to put in cultured marble in the tub/shower, on the floor and vanity top. I'll probably do something very neutral so it won't have to be torn out again for a good long while.

The plumber comes tomorrow to repipe the bathroom with copper and replace the toilet drain pipe since that seems to have been the source of many of our troubles. After it's repiped, in goes a new tub and toilet and vanity with sink.

I'll be glad when this incidental redmodel is wrapped up!

Amy
Fremont, CA

Hi Amy,
I am really glad I am not the only one having this problem!! Our toilet has also been leaking and the particle board was a mess with water rot and termites!! I ripped out the particle board and the plywood subfloor underneath doesn't appear to be too bad; can't stick a screwdriver through it. We also have support beams under the house about 4 feet apart and while there is one about 1 foot away from the toilet area, the other is 3 feet away in a whole new room! I really need to do a quick fix that will last a decent amount of time since my husband and I are selling and moving. I wanted to know if you laid down plywood on top of the existing plywood subfloor, what kind of plywood you used and what you treated it (or did you treat the subfloor?) with?? Any help from anyone would really be greatly appreciated!!!

Thanks!
Colby

In reference to the above: did you use plywood over the subfloor in place of particle board and if so, what kind, did you treat that and with what??

Thanks!
Colby

they said they used EXTERIOR GRADE PLYWOOD. in other words pressure treated plywood.

Hello!

Just thought I'd jump in here. I believe that exterrior plywood just has a better binder and a wood with a little rot resistance (like fir). For example you could get a 1/2 CDX plywood (house sheathing)- the C and the D are codes for the condition of the surface on each side of the sheet the X is for exterrior. CDX plywood is much cheaper than pressure treated and I imagine a lot less toxic as it is not chemically treated.
I would go with non pressure treated plywood or osb and fix the problem with your toilet.